Multi-speed gearbox

ABSTRACT

Transmission with four gear sets, shafts and six shift elements. Sun of first set is connected to fifth shaft, which is couplable to housing by second brake and connectable by first clutch to driveshaft, which is connectable to seventh shaft connected by second clutch to carrier of second set and is connectable by third clutch to eighth shaft connected to carrier of first set and to sun of second set. Seventh shaft is connectable to third shaft connected to ring gear of third set by fourth clutch. Sixth shaft is connected to ring gear of second set and carrier of fourth set. Fourth shaft is connected to ring gear of first set and to sun of fourth set and is couplable to housing by first brake. Sun of third set is coupled to housing. Output shaft is connected to carrier of third set and to ring gear of fourth set.

This application is a National Stage completion of PCT/EP2013/055079filed Mar. 13, 2013, which claims priority from German patentapplication serial no. 10 2012 206 774.4 filed Apr. 25, 2012.

FIELD OF THE INVENTION

The present invention relates to a multi-stage transmission of aplanetary design, in particular an automatic transmission for a motor.

BACKGROUND OF THE INVENTION

According to the prior art, automatic transmissions, particularly formotor vehicles, comprise planetary gear sets that are shifted usingfriction elements or shift elements such as clutches and brakes, andtypically are connected to a start-up element, such as a hydrodynamictorque converter or a fluid coupling, that is subject to a slip effectand is optionally provided with a lock-up clutch.

Such an automatic transmission is known, for example, from DE 199 12 480B4 by the applicant. It comprises three single-carrier planetary gearsets, as well as three brakes and two clutches for shifting six forwardgears and one reverse gear, a input shaft and an output shaft, whereinthe carrier for the first planetary gear set is continuously connectedto the ring gear of the second planetary gear set, and the carrier forthe second planetary gear set is continuously connected to the ring gearof the third planetary gear set, and the input shaft is directlyconnected to the sun gear of the second planetary gear set.

Furthermore, in the known transmission, the input shaft is connectableby means of the first clutch to the sun gear of the first planetary gearset, and by means of the second clutch to the carrier of the firstplanetary set, wherein the sun gear of the first planetary gear set isconnectable by means of the first brake to a housing of thetransmission, and the carrier of the first planetary gear set isconnectable by means of the second brake to the housing of thetransmission, wherein the sun gear of the third planetary gear set isconnectable by means of the third brake to the housing of thetransmission. The input shaft of the transmission is continuouslyconnected to the carrier for the third planetary gear set and the ringgear of the first planetary gear set.

Furthermore, a nine-speed multi-stage transmission is known from DE 2936 969 A1; it comprises eight shift elements and four planetary gearsets, wherein one planetary gear set serves as a front-mounted gear setand the main gearbox includes a Simpson set and a further planetary gearset serving as a reverse gearing.

Further multistage transmissiOns are known, for example, from theapplicant's DE 10 2005 010 210 A1 and DE 10 2006 006 637 A1.

Automatically shiftable vehicle transmissions, of a planetary design,are already generally described numerous times in the prior art and arecontinually undergoing further development and improvemeht. Thesetransmissions should have a relatively simple design, in particularrequiring a low number of shift elements, and minimize the need fordouble shifting when sequential shifting is performed, i.e., activationand/or deactivation of two shift elements, thereby ensuring that onlyone shift element is ever switched when shifting is performed in definedgroups of gears.

DE 10 2008 000 428 A1 by the applicant discloses a multi-stagetransmission of a planetary design which includes an input shaft and anoutput shaft which are disposed in a housing. With the knowntransmission, at least four planetary gear sets, hereinafter termed thefirst, second, third and fourth planetary gear sets, at least eightrotatable shafts, hereinafter termed the drive shaft, output shaft,third, fourth, fifth, sixth, seventh and eighth shaft, as well as atleast six shaft elements comprising brakes and clutches are provided,the selective engagement of which generates different transmissionratios between the driveshaft and the output shaft such that preferablynine forward gears and one reverse gear are feasible.

The first and second planetary gear sets, which are preferably designedas minus planetary gear sets, i.e., with a negative stationarytransmission, form a shiftable front-mounted gear set, wherein the thirdand fourth planetary gear sets form a main gear set.

In the known multi-stage transmission, the carriers of the first and thesecond planetary gear sets are coupled together via the fourth shaftwhich is connected to an element of the main gear set, the ring gear ofthe first planetary gear set is coupled to the sun gear of the secondplanetary gear set via the eighth shaft, which is detachably connectableto the drive shaft via the first clutch, and the sun gear of the firstplanetary gear set can be coupled to a housing of the transmission bymeans of the third shaft, via a first brake, and is detachablyconnectable to the drive shaft via a second clutch, wherein the ringgear of the second planetary gear set can be coupled to a housing of thetransmission by means of the fifth shaft via a second brake. Inaddition, the seventh shaft is constantly connected to at least oneelement of the main gear set, and can be coupled to the housing of thetransmission via a third brake, and the sixth shaft is constantlyconnected to at least one further element of the main gear set and isdetachably connectable to the drive shaft, via a third clutch; and theoutput shaft is constantly connected at least to one further element ofthe main gear set.

In the known transmission, the fourth shaft is preferably constantlyconnected to the ring gear of the third planetary gear set, the sixthshaft is constantly connected to the ring gear of the fourth planetarygear set and to the carrier of the third planetary gear set, and isdetachably connectable to the drive shaft via the third clutch.Furthermore, the seventh shaft is constantly connected to the sun gearsof the third and fourth planetary gear sets, and can be coupled to ahousing of the transmission via the third brake. In this case, theoutput drive is produced via the output shaft, which is constantlyconnected to the carrier of the fourth planetary gear set. Furthermore,the third and fourth planetary gear sets can be combined or reduced to aRavigneaux set having a common carrier and a common ring gear.

According to the prior art, the shift elements of a multistagetransmission designed in this manner, which are normally designed asmulti-disk clutches or brakes, are hydraulically actuated whichdisadvantageously leads to high hydraulic losses. To circumvent thisactuation loss, it would be particularly advantageous to use shiftelements which can be actuated, as needed, such as electromechanicallyactuatable shift elements.

Shift elements which can be actuated, as needed, can in particular beunderstood as shift elements that require no or less energy to maintainthe gear state than to change the gear state.

To enable the use of shift elements that can be actuated as needed, theshift elements, in particular the clutches, must be easily accessiblefrom the outside.

SUMMARY OF THE INVENTION

The object of the present invention is to propose a multi-stagetransmission of the initially-cited type, which has nine forward gearsand one reverse gear having a sufficient transmission ratio, in whichthe design complexity, the component stress and construction size areoptimized, and efficiency is furthermore improved. In addition, theshift elements of the transmission should be readily accessible from theoutside which enables the installation of shift elements which can beactuated, as needed. Furthermore, the transmission should be suitablefor both a standard design and front-transverse design.

Accordingly, a multi-stage transmission, according to the invention, ofa planetary design is proposed which has an input shaft and an outputshaft which are disposed in a housing. In addition, there are providedat least four planetary gear sets which are designated, in thefollowing, as the first, second, third, and fourth planetary gear sets,eight rotatable shafts which are designated, in the following, as thedrive shaft, output shaft, third, fourth, fifth, sixth, seventh, andeighth shafts, and at least six shift elements preferably designedlamellar shift elements orform-locking shift elements, comprising brakesand clutches, whose selective engagement produces different transmissionratios between the drive shaft and the output shaft, and thereforepreferably nine forward gears and one reverse gear can be realized.

The first planetary gear set of the transmission is preferably designedas a plus planetary gear set, wherein the second, third and fourthplanetary gear sets are designed as minus planetary gear sets.

As is well known, a simple minus planetary gear set comprises a sungear, a ring gear, and a carrier on which the planetary gears arerotatably carried, the planetary gears meshing with the sun gear and thering gear. As a result, when the carrier is fixed, the ring gear has adirection of rotation that is opposite that of the sun gear. Incontrast, a simple plus planetary gear set comprises a sun gear, a ringgear and a carrier, on which inner and outer planet gears are rotatablycarried, wherein all inner planet gears mesh with the sun gear and allouter planet gears mesh with the ring gear, and each inner planet gearmeshes with only one outer planet gear. As a result, when the carrier isfixed, the ring gear has the same direction of rotation as the sun gear,and a positive stationary transmission ratio results.

According to a preferred embodiment of the invention, the sun gear ofthe first planetary gear set is connected to a fifth shaft which can becoupled, by means of a second brake, to the housing of the transmissionand is detachably connectable, by means of a first clutch, to thedriveshaft, wherein the driveshaft is detachably connectable, by meansof a second clutch, to the seventh shaft connected to the carrier of thesecond planetary gear set and is detachably connectable, by means of athird clutch, to the eighth shaft which is connected to the carrier ofthe first planetary gear set and the sun gear of the second planetarygear set. The seventh shaft is detachably connectable, by means of afourth clutch, to the third shaft connected to the ring gear of thethird planetary gear set.

Furthermore, the sixth shaft is connected to the ring gear of the secondplanetary gear set and the carrier of the fourth planetary gear set,wherein the fourth shaft is connected to the ring gear of the firstplanetary gear set and the sun gear of the fourth planetary gear set,and can be coupled, by means of a first brake, to the housing.

Furthermore, the drive shaft is connected to the carrier of the thirdplanetary gear set and the ring gear of the fourth planetary gear set,wherein the sun gear of the third planetary gear set is coupled to thehousing.

Since the first, second and third clutches are disposed on thedriveshaft of the transmission, two additional switch shift elements aredesigned as brakes, and the fourth clutch, viewed radially, is disposedin proximity to the housing, ready accessibility of all of thetransmission shift elements is achieved, which allows the shift elementsto be designed as shift elements which can be actuated, as needed. Inthe context of additional embodiments of the invention, shift elementsof the transmission can be designed, inter alia, ashydraulically-actuatable shift elements.

Furthermore, transmission ratios result that are particularly suitablefor passenger vehicles, and in a greater overall gear ratio of themulti-stage transmission, thereby improving driving smoothness andsignificantly reducing fuel consumption.

In addition, design complexity is significantly reduced with themulti-stage transmission according to the invention due to a low numberof shift elements. Using the multi-stage transmission according to theinvention, it is advantageously possible to perform a start-up using ahydrodynamic converter, an external start-up clutch, or any othersuitable external start-up element. It is also conceivable to perform astart-up using a start-up element integrated in the transmission.Preferably, a shift element that is actuated in the first forward gearand in the reverse gear is suitable for this.

Moreover, the multi-stage transmission, according to the invention,results in good efficiency in the main drive gears with respect to draglosses and gearing losses.

Advantageously, low torques exist in the shift elements and in theplanetary gear sets of the multi-stage transmission, therebyadvantageously reducing wear in the multi-stage transmission. Inaddition, the low torques make it possible to utilize correspondinglylow dimensions, thereby reducing the necessary installation space andrelated costs. Furthermore, the rotational speeds of the shafts, shiftelements, and planetary gear sets are low.

In addition, the transmission, according to the invention, is designedto allow adaptability to different drive train embodiments in terms ofpower flow direction and spatial aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail in the following, as anexample, with reference to the attached Figures. They show:

FIG. 1: A schematic view of a preferred embodiment of a multi-stagetransmission according to the invention; and

FIG. 2: An example of a shift pattern for a multi-stage transmissionaccording to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a multi-stage transmission, according to the invention,which has a drive shaft 1, an output shaft 2, and four planetary gearsets P1, P2, P3 and P4 which are disposed in a housing G. The second,third and fourth planetary gear set P2, P3, P4 in the example shown inFIG. 1 are designed as minus planetary gear sets, wherein the firstplanetary gear set P1 is designed as a plus planetary gear set.According to the invention, at least one of the additional planetarygear sets P2, P3, P4 can be designed as a plus planetary gear set if thecarrier and the ring gear connections are simultaneously exchanged, andthe value of the stationary transmission ratio is increased by 1 incomparison to the design as a minus planetary gear set.

Viewed axially, the planetary gear sets P1, P2, P3, P4, in the portrayedexemplary embodiment, are disposed in the sequence of the firstplanetary gear set P1, the second planetary gear set P2, the thirdplanetary gear set P3, and the fourth planetary gear P4. According tothe invention, the actual sequence of individual planetary gear sets andthe arrangement of the shift elements are freely selectable as permittedby the connectivity of the elements.

As shown in FIG. 1, six shift elements are provided, namely, two brakes04, 05 and four clutches 15, 17, 18 and 37. The spatial disposition ofthe shift elements can be arbitrary, and is limited only by thedimensions of the outer design. The transmission's clutches and brakesare preferably designed as friction shift elements or lamellar shiftelements, but they can also be designed as form-locking shift elements.

Selective shifting of nine forward gears and one reverse gear can berealized using these shift elements. The multi-stage transmission,according to the invention, has a total of eight rotatable shafts,namely, the shafts 1, 2, 3, 4, 5, 6, 7 and 8, wherein the drive shaft isthe first shaft 1, and the output shaft is the second shaft 2 of thetransmission.

According to the invention, in the multi-stage transmission according toFIG. 1, the sun gear of the first planetary gear set P1 is connected tothe fifth shaft 5 which can be coupled, by means of a second brake 05,to the housing G of the transmission, and is detachably connectable, bymeans of a first clutch 15, to the driveshaft 1, wherein the driveshaft1 is detachably connectable, by means of a second clutch 17, to theseventh shaft 7 connected to the carrier of the second planetary gearset P2, and is detachably connectable, by means of a third clutch 18, tothe eighth shaft 8 which is connected to the carrier of the firstplanetary gear set P1 and to the sun gear of the second planetary gearset P2, wherein the seventh shaft 7 is detachably connectable, by meansof a fourth clutch 37, to the third shaft 3 connected to the ring gearof the third planetary gear set P3.

As can be seen in FIG. 1, the sixth shaft 6 is connected to the ringgear of the second planetary gear set P2 and the carrier of the fourthplanetary gear set P4, wherein the fourth shaft 4 is connected to thering gear of the first planetary gear set P1 and the sun gear of thefourth planetary gear set P4 and can be coupled, by means of a firstbrake 04, to the housing G.

Furthermore, the drive shaft 2 of the transmission is connected to thecarrier of the third planetary gear set P3 and the ring gear of thefourth planetary gear set P4, wherein the sun gear of the thirdplanetary gear set P3 is coupled to the housing G (shaft 0).

Viewed axially, the first, second and third clutch 15, 17, 18 can bedisposed next to each other and designed as lamellar shift elements, andhave a common outer clutch disc carrier. In the portrayed exemplaryembodiment, particularly the fourth clutch 37 is suitable for a designas a jaw clutch element which significantly improves usage.

FIG. 2 shows an example of a shift pattern of a multi-stage transmissionaccording to FIG. 1. Three shift elements are engaged for every gear.The shift pattern shows, as examples, the particular transmission ratiosi of the individual gear steps and, to be determined therefrom, the gearincrements or step changes φ to the next higher gear, wherein the value8.964 is the transmission ratio spread.

The values for the stationary transmission ratios of the planetary gearsets P1, P2, P3, and P4, designed as minus planetary gear sets, are1.946, −3.676, −2.767 and −2.062, respectively. FIG. 2 shows that onlyone shift element must be engaged and one shift element must bedisengaged when shifting sequentially, since two neighbouring gear stepsjointly use two shift elements. It is also shown that a largetransmission ratio spread is attained with small gear increments.

The first forward gear is attained by engaging the first brake 04 andthe third and fourth clutches 18, 37; the second forward gear isattained by engaging the second brake 05 and the third and fourthclutches 18, 37; the third forward gear is attained by engaging thefirst, third and fourth clutches 15, 18, 37; the fourth forward gear isattained by engaging the first, second and fourth clutches 15, 17, 37;the fifth forward gear, which for example is designed as a direct gear,is attained by engaging the first, second and third clutches 15, 17, 18;the sixth forward gear is attained by engaging the second brake 05 andthe second and third clutches 17, 18; the seventh forward gear isattained by engaging the first brake 04 and the second and thirdclutches 17, 18; the eighth forward gear is attained by engaging thefirst and the second brakes 04, 05 and the second clutch 17; and theninth forward gear is attained by engaging the first brake 04 and thefirst and second clutches 15, 17, wherein the reverse gear is attainedby engaging the brake 04 and the first and fourth clutches 15, 37.

Alternately, the fourth forward gear can be shifted by additionalshifting combinations which are identified in FIG. 2 with M.Accordingly, the fourth forward gear can be attained by engaging thefirst brake 04 and the second and fourth clutches 17, 37, or by engagingthe first, second and fourth clutches 15, 17, 37, or by engaging thesecond brake 05 and the second and fourth clutches 17, 37.

Since the first brake 04 and the first, third and fourth clutches 15,18, 37 are engaged in the first forward gear and/or in the reverse gear,these shift elements can be used as start-up elements.

According to the invention, different gear increments also result fromthe same gear pattern depending on the shift logic, thereby making itpossible to implement an application-specific or a vehicle-specificvariation.

According to the invention, it is furthermore optionally possible toprovide additional freewheels at each suitable location of themulti-staged transmission, for example, between a shaft and the housing,or possibly to connect two shafts.

An axle differential and/or a distributor differential can be disposedon the drive side or on the output side.

Within the scope of an advantageous development of the invention, thedrive shaft 1 can be separated from a drive motor, as needed, by aclutch element, wherein a hydrodynamic converter, a hydraulic clutch, adry start-up clutch, a wet start-up clutch, a magnetic powder clutch, ora centrifugal clutch can be used as the clutch element or the like. Itis also possible to dispose such a start-up element in the power flowdirection after the transmission wherein, in this case, the drive shaft1 is continuously connected to the crankshaft of the drive motor.

The multi-stage transmission, according to the invention, also makes itpossible to situate a torsional-vibration damper between the drive motorand the transmission.

Within the scope of a further, not represented embodiment of theinvention, a wear-free brake, for instance, a hydraulic or electricretarder or the like, can be disposed on each shaft, preferably on thedrive shaft 1 or the output shaft 2, which is of special significancefor use in commercial vehicles in particular. Furthermore, a powertake-off drive can be provided on each shaft, preferably on the inputshaft 1 or the output shaft 2, for driving additional assemblies.

The friction shift elements that are used can be designed as powershiftable clutches or brakes. In particular, force locking clutches orbrakes can be used, for instance, lamellar clutches, band brakes, and/orcone clutches.

A further advantage of the multi-stage transmission presented here isthat an electric machine can be attached to each shaft as a generatorand/or as an additional drive machine.

REFERENCE SIGNS

-   0 shaft-   1 first shaft, input shaft-   2 second shaft, output shaft-   3 third shaft-   4 fourth shaft-   5 fifth shaft-   6 sixth shaft-   7 seventh shaft-   8 eighth shaft-   04 first brake-   05 second brake-   15 first clutch-   17 second clutch-   18 third clutch-   37 fourth clutch-   G housing-   P1 first planetary gear set-   P2 second planetary gear set-   P3 third planetary gear set-   P4 fourth planetary gear set-   i transmission ratio-   φ step change

The invention claimed is:
 1. A multi-stage transmission of a planetarydesign comprising: a driveshaft (1), an output shaft (2), first, second,third and fourth planetary gear sets (P1, P2, P3, P4) which are disposedwithin a housing (G) and each of the first, the second, the third andthe fourth planetary gear sets comprises a ring gear, a carrier, planetgears and a sun gear, third, fourth, fifth, six, seventh and eighthrotatable shafts (3, 4, 5, 6, 7, 8), six shift elements (04, 05, 15, 17,18, 37) comprising brakes (04, 05) and clutches (15, 17, 18, 37), andselective engagement of the six shift elements (04, 05, 15, 17, 18, 37)generates different transmission ratios between the driveshaft (1) andthe output shaft (2) such that nine forward gears and one reverse gearare implementable, wherein the sun gear of the first planetary gear set(P1) is connected to the fifth shaft (5), the fifth shaft (5) can becoupled to the housing (G) by engagement of a second brake (05) and thefifth shaft (5) can be detachably connected, by engagement of a firstclutch (15), to the drive shaft (1), the drive shaft (1) can bedetachably connected, by engagement of a second clutch (17), to theseventh shaft (7) connected to the carrier of the second planetary gearset (P2), the drive shaft (1) can be detachably connected, by engagementof a third clutch (18), to the eighth shaft (8) which is connected toboth the carrier of the first planetary gear set (P1) and to the sungear of the second planetary gear set (P2), the seventh shaft (7) can bedetachably connected, by engagement of a fourth clutch (37), to thethird shaft (3) which is connected to the ring gear of the thirdplanetary gear set (P3), the sixth shaft (6) is connected to both thering gear of the second planetary gear set (P2) and the carrier of thefourth planetary gear set (P4), the fourth shaft (4) is connected toboth the ring gear of the first planetary gear set (P1) and to the sungear of the fourth planetary gear set (P4), and the fourth shaft (4) canbe coupled to the housing (G) by engagement of a first brake (04), thesun gear of the third planetary gear set (P3) is coupled to the housing(G), and the output shaft (2) is directly connected to both the carrierof the third planetary gear set (P3) and to the ring gear of the fourthplanetary gear set (P4).
 2. The multi-stage transmission according toclaim 1, wherein the first planetary gear set (P1) is designed as a plusplanetary gear set, and the second, the third and the fourth planetarygear sets (P2, P3, P4) are designed as minus planetary gear sets.
 3. Themufti-stage transmission according to claim 1, wherein, when viewedaxially, the first, the second, the third and the fourth planetary gearsets are disposed in a sequence of the first planetary gear set (P1),the second planetary gear set (P2), the third planetary gear set (P3)and the fourth planetary gear set (P4).
 4. The mufti-stage transmissionaccording to claim 1, wherein the shift elements (03, 04, 05, 15, 17,18) of the transmission are designed as shift elements which can beactuated as needed.
 5. The multistage transmission according to claim 1,wherein the fourth clutch (37) is designed as a form-locking shiftelement.
 6. The multi-stage transmission according to claim 1, whereinthe first forward gear is attained by engaging the first brake (04) andthe third and the fourth clutches (18, 37); the second forward gear isattained by engaging the second brake (05) and the third and the fourthclutches (18, 37); the third forward gear is attained by engaging thefirst, the third and the fourth clutches (15, 18, 37); the fourthforward gear is attained by engaging the first, the second and thefourth clutches (15, 17, 37); the fifth forward gear is attained byengaging the first, the second and the third clutches (15, 17, 18); thesixth forward gear is attained by engaging the second brake (05) and thesecond and the third clutches (17, 18); the seventh forward gear isattained by engaging the first brake (04) and the second and the thirdclutches (17, 18); the eighth forward gear is attained by engaging thefirst and the second brakes (04, 05) and the second clutch (17); theninth forward gear is attained by engaging the first brake (04) and thefirst and the second clutches (15, 17); and the reverse gear is attainedby engaging the first brake (04) and the first and the fourth clutches(15, 37).
 7. The multi-stage transmission according to claim 1, whereinthe first forward gear is attained by engaging the first brake (04) andthe third and the fourth clutches (18, 37); the second forward gear isattained by engaging the second brake (05) and the third and the fourthclutches (18, 37); the third forward gear is attained by engaging thefirst, the third and the fourth clutches (15, 18, 37); the fourthforward gear is attained by engaging the first brake (04) and the secondand the fourth clutches (17, 37); the fifth forward gear is attained byengaging the first, the second and the third clutches (15, 17, 18); thesixth forward gear is attained by engaging the second brake (05) and thesecond and the third clutches (17, 18); the seventh forward gear isattained by engaging the first brake (04) and the second and the thirdclutches (17, 18); the eighth forward gear is attained by engaging thefirst and the second brakes (04, 05) and the second clutch (17); theninth forward gear is attained by engaging the first brake (04) and thefirst and the second clutches (15, 17); and the reverse gear is attainedby engaging the first brake (04) and the first and the fourth clutches(15, 37).
 8. The multi-stage transmission according to claim 2, whereinthe first forward gear is attained by engaging the first brake (04) andthe third and the fourth clutches (18, 37); the second forward gear isattained by engaging the second brake (05) and the third and the fourthclutches (18, 37); the third forward gear is attained by engaging thefirst, the third and the fourth clutches (15, 18, 37); the fourthforward gear is attained by engaging the first, the second and thefourth clutches (15, 17, 37); the fifth forward gear is attained byengaging the first, the second and the third clutches (15, 17, 18); thesixth forward gear is attained by engaging the second brake (05) and thesecond and the third clutches (17, 18); the seventh forward gear isattained by engaging the first brake (04) and the second and the thirdclutches (17, 18); the eighth forward gear is attained by engaging thefirst and the second brakes (04, 05) and the second clutch (17); theninth forward gear is attained by engaging the first brake (04) and thefirst and the second clutches (15, 17); and the reverse gear is attainedby engaging the first brake (04) and the first and the fourth clutches(15, 37).
 9. The multi-stage transmission according to claim 1, whereinthe first forward gear is attained by engaging the first brake (04) andthe third and the fourth clutches (18, 37); the second forward gear isattained by engaging the second brake (05) and the third and the fourthclutches (18, 37); the third forward gear is attained by engaging thefirst, the third and the fourth clutches (15, 18, 37); the fourthforward gear is attained by engaging the second brake (05) and thesecond and the fourth clutches (17, 37); the fifth forward gear isattained by engaging the first, the second and the third clutches (15,17, 18); the sixth forward gear is attained by engaging the second brake(05) and the second and the third clutches (17, 18); the seventh forwardgear is attained by engaging the first brake (04) and the second and thethird clutches (17, 18); the eighth forward gear is attained by engagingthe first and the second brakes (04, 05) and the second clutch (17); theninth forward gear is attained by engaging the first brake (04) and thefirst and the second clutches (15, 17); and the reverse gear is attainedby engaging the first brake (04) and the first and the fourth clutches(15, 37).
 10. The multi-stage transmission according to claim 1, whereinthe multi-stage transmission is an automatic transmission for a motorvehicle.
 11. A multi-stage transmission of a planetary designcomprising: a driveshaft, an output shaft, first, second, third andfourth planetary gear sets which are disposed in a housing, and each ofthe first, the second, the third and the fourth planetary gear setscomprises a ring gear, a carrier, planet gears and a sun gear, third,fourth, fifth, six, seventh and eighth rotatable shafts, six shiftelements comprising brakes and clutches, and selective engagement of thesix shift elements generates different transmission ratios between thedriveshaft and the output shaft such that nine forward gears and onereverse gear are implementable, wherein the sun gear of the firstplanetary gear set is connected to the fifth shaft, the fifth shaft canbe coupled to the housing by engagement of a second brake and the fifthshaft can be detachably connected, by engagement of a first clutch, tothe drive shaft, the drive shaft can be detachably connected, byengagement of a second clutch, to the seventh shaft connected to thecarrier of the second planetary gear set, the drive shaft can bedetachably connected, by engagement of a third clutch, to the eighthshaft which is connected to both the carrier of the first planetary gearset and to the sun gear of the second planetary gear set, the seventhshaft can be detachably connected, by engagement of a fourth clutch, tothe third shaft which is connected to the ring gear of the thirdplanetary gear set, the sixth shaft is connected to both the ring gearof the second planetary gear set and the carrier of the fourth planetarygear set, the fourth shaft is connected to both the ring gear of thefirst planetary gear set and to the sun gear of the fourth planetarygear set, and the fourth shaft can be coupled to the housing byengagement of a first brake, the sun gear of the third planetary gearset is coupled to the housing, and the output shaft is directlyconnected to both the carrier of the third planetary gear set (P3) andto the ring gear of the fourth planetary gear set (P4).
 12. Themulti-stage transmission according to claim 11, wherein the multi-stagetransmission is an automatic transmission for a motor vehicle.
 13. Themulti-stage transmission according to claim 11, wherein the firstforward gear is attained by engaging the first brake and the third andthe fourth clutches; the second forward gear is attained by engaging thesecond brake and the third and the fourth clutches; the third forwardgear is attained by engaging the first, the third and the fourthclutches; the fourth forward gear is attained by engaging the first, thesecond and the fourth clutches; the fifth forward gear is attained byengaging the first, the second and the third clutches; the sixth forwardgear is attained by engaging the second brake and the second and thethird clutches; the seventh forward gear is attained by engaging thefirst brake and the second and the third clutches; the eighth forwardgear is attained by engaging the first and the second brakes and thesecond clutch; the ninth forward gear is attained by engaging the firstbrake and the first and the second clutches; and the reverse gear isattained by engaging the first brake and the first and the fourthclutches.
 14. The mufti-stage transmission according to claim 11,wherein the first forward gear is attained by engaging the first brakeand the third and the fourth clutches; the second forward gear isattained by engaging the second brake and the third and the fourthclutches; the third forward gear is attained by engaging the first, thethird and the fourth clutches; the fourth forward gear is attained byengaging the first brake and the second and the fourth clutches; thefifth forward gear is attained by engaging the first, the second and thethird clutches; the sixth forward gear is attained by engaging thesecond brake and the second and the third clutches; the seventh forwardgear is attained by engaging the first brake and the second and thethird clutches; the eighth forward gear is attained by engaging thefirst and the second brakes and the second clutch; the ninth forwardgear is attained by engaging the first brake and the first and thesecond clutches; and the reverse gear is attained by engaging the firstbrake and the first and the fourth clutches.
 15. The multi-stagetransmission according to claim 12, wherein the first forward gear isattained by engaging the first brake and the third and the fourthclutches; the second forward gear is attained by engaging the secondbrake and the third and the fourth clutches; the third forward gear isattained by engaging the first, the third and the fourth clutches; thefourth forward gear is attained by engaging the first, the second andthe fourth clutches; the fifth forward gear is attained by engaging thefirst, the second and the third clutches; the sixth forward gear isattained by engaging the second brake and the second and the thirdclutches; the seventh forward gear is attained by engaging the firstbrake and the second and the third clutches; the eighth forward gear isattained by engaging the first and the second brakes and the secondclutch; the ninth forward gear is attained by engaging the first brakeand the first and the second clutches; and the reverse gear is attainedby engaging the first brake and the first and the fourth clutches. 16.The multi-stage transmission according to claim 1, wherein the firstforward gear is attained by engaging the first brake and the third andthe fourth clutches; the second forward gear is attained by engaging thesecond brake and the third and the fourth clutches; the third forwardgear is attained by engaging the first, the third and the fourthclutches; the fourth forward gear is attained by engaging the secondbrake and the second and the fourth clutches; the fifth forward gear isattained by engaging the first, the second and the third clutches; thesixth forward gear is attained by engaging the second brake and thesecond and the third clutches; the seventh forward gear is attained byengaging the first brake and the second and the third clutches; theeighth forward gear is attained by engaging the first and the secondbrakes and the second clutch; the ninth forward gear is attained byengaging the first brake and the first and the second clutches; and thereverse gear is attained by engaging the first brake and the first andthe fourth clutches.